Land-tracts during the Secondary and Tertiary periods. 163 



Jurassic and lower cretaceous deposits apparently fill are found 

 to be traversed by anticlinals of anterior origin *, which formed 

 either peninsulas or islands in the Jurassic and Neocomian seas 

 that occupied the South-east of England, and parts of France and 

 Belgium, during the formation of those deposits. 



Further, we find, in the case of deposits since the palaeozoic 

 period, that almost all of them have been formed in the neigh- 

 bourhood of land which has supplied the material for their com- 

 position. There are exceptions, such as the cretaceous and the 

 nummulitic series of Europe and Asia ; but even these fall far 

 short of what we should conceive to be the bed of a great ocean, 

 such as the Pacific, were it the case that deposits took place in it 

 of a thickness sufficient to ensure their preservation on upheaval. 

 It has been remarked by Mr. Darwin (Origin of Species, pp. 300 

 and 343) that seas have been seas, and continents have been 

 continents, for periods far greater, geologically speaking, than 

 we have been apt to assign for their existence. 



In applying these principles to elucidate the broader features 

 of the geographical configuration at any geological period, we 

 have to bear in mind another and even more important fact, viz. 

 the permanence through vast periods of the general direction of 

 the lines of volcanic eruption over a whole hemisphere: I shall 

 at a later stage of this paper enter into some detail upon this 

 subject, and therefore only refer here to the fact of this perma- 

 nence. Consider the chain of the Andes forming a line of vol- 

 canic eruption more or less active through near 60 degrees of the 

 earth's circumference, and prolonged for an equal distance by the 

 chain of the Rocky Mountains, and the almost continuous vol- 

 canic band extending from the Azores in a south-easterly direc- 

 tion to the centre of the Pacific, and we see that the development 

 of volcanic eruptions has been exhibited with a permanence and 

 persistency of direction over immense areas, and may therefore 

 well assume that the influence of this persistence upon the geo- 

 graphical configuration of the period during which it prevailed 

 must have been, perhaps beyond all other things, important and 

 enduring. Into the causes of this persistency of direction during 

 long periods I do not pretend here to enter, further than to 

 remark upon the insufficiency of the adventitious action of per- 

 colated water upon the metallic bases to account for it. The fact 

 so often mooted, of the contiguity of all active volcanoes to the 

 sea or to great inland waters, is not only explicable on othe 

 grounds, but is, I venture to suggest, the necessary concomitant 

 of any elevatory action acting spasmodically like that of volcanoes. 



• See Prestwich, Quart. Journ. Geol. Soc. vol. xii. p. 10 ; also vol. xiv 

 p. 250; and Degousee and Laurent, Quart. Journ. Geol. Soc. vol. xii. 

 p. 252. 



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